Article,
A Genome-Wide Analysis Reveals No Nuclear Dobzhansky-Muller Pairs of Determinants of Speciation between S. cerevisiae and S. paradoxus, but Suggests More Complex Incompatibilities
PLoS Genet, 6 (7): e1001038 (July 2010)
DOI: 10.1371/journal.pgen.1001038
Abstract
Species are defined such that organisms of the same species can produce fertile offspring, whereas organisms of different species are either unable to mate, or when they do, they produce inviable or sterile progeny. A well-known pair of species that can mate yet produce sterile offspring is the horse and donkey, which produce an infertile hybrid, the mule. A long-standing idea for the species barrier is that when certain pairs of genes from the two different species are combined, the genes can no longer function properly, thus causing death or sterility. Identification of these incompatible genes may allow us to determine how organisms form distinct species, and understand the process of speciation itself. We used two closely related yeasts to look for these incompatible genes by isolating rare viable hybrid offspring, and looking for excluded gene combinations. We did not find any pairs of incompatible genes, but instead found that there appear to be more than two genes involved in such incompatibilities. We speculate that the accumulation of large numbers of sequence differences in their DNA may cause defects in how genes are controlled in hybrids, causing these two yeasts to be independent species.
